I. Field
The present invention relates generally to data communication, and more specifically to techniques for using two or more modulation schemes in a single communication system.
II. Background
Wireless communication systems are widely deployed to provide various types of communication such as voice, data, and so on. These systems may be multiple-access systems, having unique modulation schemes, capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, universal mobile telecommunication system (UMTS) using wideband code divisional multiple access (WCDMA), and orthogonal frequency division multiple access (OFDMA) systems. Typically, a wireless communication system comprises several base stations, wherein each base station communicates with a mobile station using a forward link and a preset modulation scheme, and each mobile station communicates with a base station using a reverse link and a preset modulation scheme. A wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations.
Thus, there is a need in the art for techniques that use the benefits of CDMA communication system with OFDMA communication system.